Studies of the conformation of cholesteryl esters in pure phases will be undertaken using specific deuteration combined with neutron scattering measurements. Deuterium atoms placed in the tail of the cholesterol molecule and in the terminal methyl group of the fatty acid chain will provide an interference signal which will report the separation of these two molecular regions. This will permit documentation of the conformations present in the smectic, isotropic, and cholesteric phases of cholesteryl myristate. Continued study of the influence of the state of model droplets on the activity of cholesteryl ester hydrolase will be carried out. We hope to ascertain whether the different liquid crystal mesophases influence the activity of enzymes which have as their substrates cholesteryl esters. Studies have been initiated which exploit nuclear magnetic resonance to study the compositional determinants of phases present in intact aortas. Preliminary indications show that Carbon 13 NMR will be a forceful tool in this regard, and we hope to extend our studies to proton measurements as well.